1. Field of the Invention
The present invention relates to an all-weather braking aid for a vehicle having air pressure brakes. In particular, the present invention relates to an all-weather braking aid for air pressure brakes providing controlled intermittent braking to avoid brake lock-up and overheating.
2. Prior Art
Brake problems on vehicles may be caused by a number of factors. During wet or other difficult road conditions, brakes may lock with the result that the vehicle goes out of control. Brake problems may also arise from overheating of the brakes when used in long declines.
It is possible to a certain extent for a driver to learn the skill of alternately applying and releasing the brakes to avoid locking the wheels and causing a skid. Also, in a panic situation, the driver's normal reaction is to apply full pressure, causing lock-up, skidding and possible jack-knifing.
Anti-lock all-weather braking aids have been proposed in the past. Some of the systems are operational by monitoring the turning of the individual wheels and feedback loop circuitry to predict impending wheel lock-up.
Russell (U.S. Pat. No. 4,538,859) discloses a system which is activated by both the driver and the inertia of the vehicle. When the brake pedal is depressed past half-way, the system is inoperative. This system becomes inoperative when hard braking, or panic stop, are required, making the system go into conventional braking, due to brake pressure applied to the brake pedal which activates the plunger to disable the pulsating on and off switch, which is controlled by foot brake air pressure. This causes conventional braking to be in effect, when the anti-lock action is badly needed.
Other A.B.S.'s (Anti-Lock Brake Systems) presently on the market monitor individual wheel speeds through wheel speed sensors monitored by an on-board computer. In operation, if any wheel(s) is/are slowing rapidly, indicating impending lock-up, air pressure to that/those brake actuator chamber(s) is "dumped" or vented to atmosphere. This allows several undesirable things to happen: (1) the wheels that are still being braked will, in turn, approach lock-up, and air pressure will be dumped from those chambers, sequentially; (2) this "hunting" action repeats, rapidly, causing alternating wheels to rapidly roll free, then brake. The driver has no control over wheels.
A need remains for a reliable vehicle all-weather braking aid which will provide intermittent controlled braking for air pressure brakes to avoid wheel locking and skidding and to avoid overheating of the vehicles brakes.
Accordingly, it is a principal object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brakes which will provide controlled intermittent braking activated by the inertia of the vehicle.
It is a further object and purpose of the present invention to provide a vehicle all-weather braking aid that can easily and inexpensively be added to existing air pressure brake systems.
It is an additional object and purpose of the present invention to provide a vehicle all-weather braking aid that is responsive to both forward and lateral inertia of the vehicle.
It is a further object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brake systems that will reduce tire and mechanical brake assembly wear.
It is a further object and purpose of the present invention to provide a vehicle all-weather braking aid which will use less air and will maintain an increased volume of air to provide additional reserve supply of air, and in consuming less air, the vehicle's air compressor will not work as hard, thereby reducing wear and maintenance. This is extremely important on long steep downgrades that require excessive air usage.
Still further it is an object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brakes that will provide improved front steering wheel braking without any lock-up or skidding or loss of steering control, during normal braking and in emergency or panic stops, on dry or wet roads.
It is an additional object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brake systems that will provide improved rear wheel braking without any lock-up or skidding, during normal braking and in emergency or panic stops, on dry or wet roads.
It is a further object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brakes that will provide improved air volume and pressure management of the vehicle's air capacity, i.e., the vehicle stopping effort will be improved while, at the same time, less application air pressure will be required, thus saving the vehicle's air supply, and allowing the vehicle to descend longer down-grades without loss of adequate air pressure supply volume.
It is an additional object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brake systems that will provide improved braking at a reduced application air pressure, so that the driver can effectively slow and stop the vehicle with less foot pressure on the brake pedal valve than is possible without the aid. Vehicle air supply usage is thereby reduced.
It is a further object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brakes that, by pulsing the brakes, will accomplish less wear of the brakes linings and brake drums while improving the stopping power of the vehicle, thereby reducing operating costs.
It is an additional object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brakes that will improve stopping power while at the same time reducing heat build-up of the brake linings and brake drums, thereby reducing brake fade and brake glazing, both detrimental to safe operation of the vehicle.
It is an additional object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brakes that is activated by either forward or lateral inertia of the vehicle in the normal mode and may optionally be manually activated by a secondary switch mechanism for hazardous road conditions.
It is an additional object and purpose of the present invention to provide a vehicle all-weather braking aid for air pressure brakes that operates equally on either a tractor, trailer or both.